The BBC is mostly liberal, rather than left, though they have devoted a lot of time to appear balanced by appeasing the right. Hence why figures like Farage became ubiquitous without UKIP having any elected MPs at the time* and only interviewing Le Pen in the French elections. I fail to see some left wing agenda when they do stuff like this.
*Compare and contrast that with how the Greens get coverage when they do have an MP and more councillors now.